package day.day7_1;

import java.util.Scanner;

public class Main{
    public static void main(String[] args) {
        //通过分析，满足条件的有（x1=x2且y1-y2=0）和（x1-x2=0且y1=t2）两种情况
        Scanner sc=new Scanner(System.in);
        int w=sc.nextInt();
        int h=sc.nextInt();
        int count=0;
        //借用二维数组存储坐标
        int[][] arr=new int[w][h];
        for (int i = 0; i < w; i++) {
            for (int j = 0; j <h ; j++) {
                if (arr[i][j]==0){
                    count++;
                    if (i+2<w){
                        arr[i+2][j]=1;
                    }
                    if (j+2<h){
                        arr[i][j+2]=1;
                    }
                }
            }
        }
        System.out.println(count
        );
    }
}

